Mold grows in and in so if it's too old you may have to have a pro do the removal.
I have found TILEX or bleach usually works. Let is sit and do not breath in the fumes.
Rinse later.

We've been using the Dow Scrubbing Bubbles products for years, and their Automatic Shower Sprayer unit is absolutely fantastic for keeping the shower and tile and grout spotless. You just push the button after showering, it beeps and gives you 15 seconds or so to get out and close the door/curtain and it sprays the liquid 360 degress. That is it.

I use Chlorox whenever possible, but this is far better for keeping the shower clean.....far less toxic and you don't have to handle anything or be near it breathing fumes when it sprays. You can leave the room before it sprays.

Our shower is 4 years old and the grout is sparkling white like brand new.

See:
http://www.scrubbingbubbles.com/Prod...r-cleaner.aspx

Be careful with this product. Friends with a home in Hadley had this in their guest shower/tub and it dripped onto the faucet. The finish on the faucet is ruined.

Just an fyi, when we moved in our new home tour guide mentioned that we should always leave the exhaust fan on for a while after showering so as to pull out the extra moisture. We do that and we also squeegee the walls and floors after each shower. No mold. Takes a little time but it works.

Mold Armour has TWO products.... the bottles look the same. One is a mold remover, one is a mold preventative. You probably got the preventative by mistake.... the remover is more expensive ($7.99-11.99)